As shown in FIG. 1, a typical fuel injector 20 has a swirl generator 40 to impart a swirl force to injected fuel. The swirl generator 40 includes an inner member and an outer member that cooperatively define a plurality of fuel passageways and impart the swirl force to injected fuel. The outer member is fixed to a body of the fuel injector 20, and the inner member is rotatably inserted into a center hole of the outer member. A knob 60 is connected to the inner member, and thereby the inner member can be rotated by rotating the knob 60.
The fuel injector 20 includes a fuel inlet portion 12, a fuel outlet portion 14 and a fuel passageway 16.
If the inner member is rotated, the shape of the fuel passageways changes so that the amount of swirl force imparted to the injected fuel can be regulated.
In such a fuel injector, a rotator such as a motor is needed to rotate the knob. The rotator is disposed outside the fuel injector and is controlled by an electronic control unit (ECU). To control the fuel injector, the fuel injection timing, fuel injection duration, fuel pressure, and an axial position of the inner member need to be controlled. However, these parameters are not considered in general ECU control, and thus to control the fuel injector, the whole ECU control should be changed.
Further, because an intake manifold is disposed near the fuel injector, it is very difficult to dispose a motor proximate to the injector to control the axial position of the inner member. A recent tendency in the intake manifold is to widen its sectional area to minimize the loss of intake flow, and therefore it is much more difficult to secure a space for mounting the motor.
Furthermore, in a gasoline direct injection (GDI) engine, a valve for strengthening tumble or a valve for controlling the amount of swirl force is installed in the intake manifold for obtaining a strong intake flow at a low speed and a low load. Therefore, resistance force against intake air becomes larger than in a multi point injection (MPI) engine because the valve installed in the intake manifold disturbs air flow. For this reason, the sectional area of the intake manifold needs to be widened for better volume efficiency and better maximum torque output. Thus, available empty space near the intake manifold becomes much smaller.
In summary, it is difficult to secure space near the intake manifold and fuel injector for mounting means for regulating the amount of swirl force imparted to the injected fuel, and manufacturing cost becomes larger for an extra drive means and an extra ECU channel.